Merge #746: Improved meteor update notice

app/meteor/update.js

@@ -14,7 +14,8 @@ var _ = require('underscore');
 
 // refuse to update if we're in a git checkout.
 if (files.in_checkout()) {
-  console.log("This is a git checkout. Update it manually with 'git pull'.");
+  console.log("Your Meteor installation is a git checkout. Update it " +
+              "manually with 'git pull'.");
   process.exit(1);
 }